Bucket positioning device utilizing a biased proximity switch

ABSTRACT

In a loader having a bucket pivotably supported upon a lift frame, tilt jacks interconnected between the lift arms and bucket by tilt linkage and a detented control valve by which the tilt jack is operated. A biased proximity switch and actuating magnet are positioned respectively upon the cylinder and rod of the tilt jack for disengaging the control value from a detented position as the bucket approaches its load position.

0 United States Patent [151 3,659,734 Fuzzell 1 May 2, 1972 54 v BUCKET POSITIONING DEVICE 3,320,562 5/1967 Germanton ..335/207 12 A IA P T 3,403,363 9/1968 Pearse et al... ..335/206 X g g i g B SED ROXINH Y 3,432,057 3/1969 Goth ..2l4/764 [72] Inventor: Joe E. Fuzzell, Peoria, 111. FOREIGN PATENTS OR APPLICATIONS 54,872 3/1968 Poland ..335/206 [73] Assgnee' Tram 1,404,208 5/1965 France ..335/207 [22] Filed: June 9, 1971 Primary ExaminerBernard A. Gilheany [21] App! l51s9l Assistant Examiner-R. N. Envall, .lr.

Related US. Application Data [57] ABSTRACT [62] Division of Ser. No. 812,829, Apr. 2, 1969, abandoned. In a loader having a bucket plvotably supported upon a llft frame, tilt jacks interconnected between the lift arms and 52 U.S. Cl ..2l4/764, 214/776, 335/207 bucket by linkage and a tented COMO] valve by which [51] Int C] "1302; 5/14 1502f 3/70 Eo2f 3/28 the tilt jack is operated. A biased proximity switch and actuat- [58] Field of Search ..335/20s-207; s magnet are Position:d respectively P the Cylinder and 214/764 776 rod of the tilt jack for disengaging the control value from a detented position as the bucket approaches its load position. [56] References Cited 5 Claims, 18 Drawing Figures RESERVOIR INVENTOR JOE E. FUZZELL AT TORN EYS Patented May 2, 1972 4 Shee ts-Sheet 5 INVENTOR JOE E. FUZZELL I w 0%,; ATTORNEYS BUCKET POSITIONING DEVICE UTILIZING A BIASED PROXIMI'I'Y SWITCH This application is a division of application Ser. No. 812,829; now abandoned.

The present invention relates to a proximity switch and more particularly to a magnetically responsive switch including biasing means which permit the switch to be maintained in more than one operating position. The present switch assembly is described below having reference to the control circuit for a loader bucket wherein the present invention is particularly adaptable. However, it will be apparent that the loader bucket control circuit represents only an exemplary environment for the switch and that the switch assembly of the present invention is readily adaptable to many other applications.

Proximity switches of the type being responsive. to a control magnet are well known in the prior art. Such a switch assembly may typically include a reed switch, for example, which is normally open. The switch is closed by placing a control magnet in close proximity to the switch so that magnetic flux from the control magnet passes through the reeds and urges them into contact with each other. The switch, however, is closed only while the control magnet remains in close proximity to the switch. As soon as the control magnet is moved away from the switch, the switch tends to return to its normally opened position. I

A proximity switchof this type is described within the control circuit for a loader bucket in US application, Ser. No. 770,670, now 11.8. Pat. No. 3,519,155 filed by Charles R. Jefferson, et al. on Oct. 25, 1968 and assigned to the assignee of the present invention. Consideration of the present switch assembly used within such a control circuit illustrates numerous advantages of the present switch assembly in comparison with the prior art. For example, the switch and control magnet may be mounted on relatively reciprocating parts of the bucket linkage with the switch to be actuated by the magnet when the bucket is in a selected position. In certain situations, examplesof which are described in greater detail below, it is desirable that the switch be maintained in its actuated condition over a range of bucket positions. With the prior art proximity switches of the type described above, it is necessary to provide a substantially elongated magnet so that a portion of the magnet remains in close proximity with-the switch throughout the selected range of bucket position. The elongated magnet tends to complicate construction of the control circuit. The characteristics of these switches further tend to limit the number of applications wherein such proximity switches may be employed.

To overcome problems of the type set forth above, it is accordingly an object of the present invention to provide a biased proximity switch permitting greater versatility its manner of use.

It is also a particular object of the present invention to provide a proximity switch which may be maintained in more than one operating position even when a control magnet is not in close proximity thereto.

It is a still further object of the invention to provide a proximity switch of a type which may be placed in one operating position by passing a control magnet in close proximity to the switch in one direction and which may be placed in a second position by passing the control magnet in close proximity to the switch in an opposite direction of travel.

It isalso an object to provide a proximity switch of the type referred to above wherein sequential operation of the switch may be accomplished through the use of a plurality of control magnets.

It is another object of the invention to provide a proximity switch suitable for use in a control circuit for regulating operation of a loader bucket.

Additional objects and advantages of the present invention are made apparent in the following description having reference to the accompanying drawings.

In the drawings:

a FIG. 1 illustrates the forward portion of a bucket loader and a partially schematic representation of a control circuit for the loader bucket as an exemplary environment for the present invention;

FIGS. 2 and 3 schematically illustrate different embodiments of control circuits within which the proximity switch of the present invention may be employed;

FIGS. 4-7 illustrate an embodiment of the present proximity switch and provide a sequential representation of the manner in which the switch is actuated by movement of a control magnet therepast;

FIGS. 8 and 9 illustrate a variation of the proximity switch assembly of FIGS. 4-7;

FIGS. 10-13 illustrate another variation of the switch assembly and similarly provide a sequential representation of the switch operation; and FIGS. l4-18 illustrate yet another variation of the switch assembly wherein a plurality of control magnets are employed to accomplish selected sequential operation of the switch with the combination of figures sequentially illustrating operation of the switch by the control magnet.

An exemplary environment for the present invention is illustrated in FIG. -1. Having reference to FIG. 1, a bucket loader vehicle 11 has an ejector bucket 12 pivotably supported at 13 upon a pair of lift arms, one of which is indicated at 14. A tilt motor or hydraulic jack having a cylinder 16 and extendible rod 17 is interconnected between each of the lift arms 14 and the bucket 12 by means of tilt linkage which includes a pair of levers with the bucket 12. Raising and lowering of the bucket is accomplished by lift jacks, one of which is indicated at 15, interconnected between the vehicle and lift arm 14.

A control circuit or system for operating the bucket and particularly for operating the tilt jacks l6 is illustrated by the schematic portion of the drawing as indicated at 26. A tilt control valve 27 includes a spool 28 which is positioned by a lever 29 to selectively communicate hydraulic fluid under pressure from a pump 31 and inlet conduit 32 into the head and rod ends of the cylinder'16 through respective conduits 33 and 34.

The bucket 12 may be racked back or pivoted in a counterclockwise direction as viewed in FIG. 1 by shifting the lever 29 and spool 28 to the position indicated at R. With the spool in this position, fluid from the conduit 32 is directed to the rod end of the cylinder 16 through the conduit 34 so that the rod 17 tends to be retracted within the cylinder 16. With the lever 29 and spool 28 shifted to a position indicated at D, fluid is directed through the conduit 33 to the head end of the cylinder 16 so that the rod 17 is extended and the bucket is moved in clockwise fashion as viewed in FIG. 1. The lever 29 and spool 28 may also be moved into a centered position indicated at 1-1 wherein both ends of the cylinder 16 are isolated from the fluid circuit so that the tilt jack I6 is prevented from moving the bucket.

Within such a control circuit, it is desirable that the operator be able to position the lever 29 for selected pivotal movement of the bucket and then direct his attention to operation of the vehicle while tilting movement of the bucket is automatically terminated during selected portions of a loading cycle. To commence a typical loading cycle, the bucket is placed in a position as illustrated in FIG. 1. The vehicle is then driven forwardly to load material into the bucket. As is common in such operations, the bucket is then alternately raised by the lift jack 1!. and racked back by the tilt jack 16 in order to accomplish more complete loading of the bucket. This operation is commonly referred to as fishtailing of the bucket. When complete loading of the bucket is assured, it is then completely racked back to a carry position (not shown) and raised by the lift jacks 15 to a position suitable for dumping. With the bucket then positioned over a transport vehicle, for example, the bucket is pivoted forwardly or in clockwise fashion beyond the position shown in FIG. 1 to unload material from the bucket.

18,19 and a link 21 connecting the forward lever 19 When the above cycle is completed, the operator may be fully occupied with steering the vehicle and returning it to a loading site to commence a new loading cycle. Accordingly, it is desirable that he is able to position the lever 29 and have the bucket automatically return to its loading position illustrated in FIG. 1. At this point, it is noted that it would be similarly desirable to provide automatic controls for the lift jack in order to permit fully automatic return of the bucket to its loading position. A similar control circuit could be employed for the lift jacks as for the tilt jacks. Accordingly, the control circuit for the lift jacks is not shown for the purpose of simplifying the specification of the present application.

To pennit automatic operation of the tilt controls, a detent mechanism 36 is associated with the lever 29. The detent mechanism includes a roller 37 mounted upon a pivotable lever 38. The lever is urged leftwardly, as seen in the drawing, by a spring 39 for engaging the roller 37 with detent notches 41 defined in the lever 29. When the lever 29 is moved to either of the positions indicated at R and D, the roller 37 is accordingly engaged with one of the notches 41. To release the detent roller from the lever 29, a slave cylinder 42 has its spool 43 linked to the lever 38. Introduction of fluid under pressure from a conduit 44 into the slave cylinder urges the spool 43 rightwardly to pivot the lever 38 and release the roller 37 from one of the notches 41. Communication of fluid through the conduit 44 is regulated by a solenoid operated, spring loaded valve 46. Normally, the valve 46 is positioned by its spring to prevent the communication of fluid to the slave cylinder 42. In this condition, the detent roller 37 is free to engage the lever 29 under the influence of spring 39. However, upon actuation of the solenoid valve, it directs fluid through the conduit 44 to the slave cylinder 42 so that the lever 38 is pivoted rightwardly to prevent detent engagement of the roller 37 with the lever 29.

The present invention particularly relates to a proximity switch which may be adapted for use in the bucket support linkage to selectively actuate the solenoid valve 46. The proximity switch assembly indicated at 50, described in greater detail, includes a magnetically responsive switch 51 supported by a bracket 52 extending forwardly from the cylinder 16 and a control magnet 53 which is secured to the extendible rod 17. The switch 51 is electrically connected in series with the solenoid 46 and a DC electrical source indicated at 54. The series connection with the source 54 also includes a normally open pressure switch 56 and a master switch 57 which controls the complete electrical circuit for the loader vehicle 11. The switch 56 remains closed during operation of the vehicle 11 but automatically functions to break the circuit with the solenoid 46 in the event the machine 11 is shut down while the switch 51 is in a closed position.

Referring again to the proximity switch assembly 50, the switch 51 is normally open at least when the control magnet 53 is positioned substantially to the right of the switch 51 as seen in FIG. 1. With the switch 51 in its normally open position, the solenoid valve 46 is positioned by its spring so that the detent roller 37 is permitted to engage the lever 29. As the rod 17 is retracted and the magnet 53 is moved into the position shown in FIG. 1, the switch 51 is caused to close and actuate the solenoid valve 46. The switch 51 remains in this closed position as the magnet 53 moves leftwardly past the switch 51. When the rod 17 is again extended and the magnet 53 approaches the switch 51 in a rightward direction as viewed in FIG. 1, the switch 51 is again caused to open. As the magnet 53 then moves rightwardly past the switch 51, the switch remains in its open position, thus, permitting the detent mechanism 36 to efiectively engage the lever 29.

Utility of the switch assembly 50 is particularly apparent upon considering the loading cycle described above. Upon dumping the bucket, it tends to be in a position pivoted forwardly or clockwise from its position shown in FIG. 1, with the rod 17 being extended and the magnet 53 moving rightwardly away from the switch 51. At this point, the lever 29 is moved into its rack back position indicated at R with the lever being engaged by the detent mechanism 36 to hold it in that position. As the bucket is pivoted toward the position indicated in FIG. 1, the magnet 53 also approaches the switch 51 and causes it to close, thus actuating the solenoid 46 and releasing the detent mechanism 36 from the lever 29. The bucket is thus automatically positioned to commence a new loading cycle. Further, as the operator intermittenly operates the tilt control lever 29 into its rack back position during the fishtailing" operation described above, the magnet is moving leftwardly away from the switch so that the switch remains in its closed position. Thus, the operator need not manually overpower the detent mechanism 36 each time he operates the tilt control lever 29 during this portion of the loading cycle.

One embodiment of the proximity switch assembly 50 is illustrated in FIGS. 4-7. Referring to those figures, the magnetically responsive switch 51 may be a reed type switch having a pair of generally parallel reeds 61 and 62 which tend into an open position as illustrated in FIG. 4. Biasing means such as the magnet indicated at 63 is associated with the switch 51. The biasing means are eflective to'maintain the switch 51 in a second or closed position once the switch is moved into that position in a manner described below. As shown in the figure, the biasing magnet 63 is generally parallel with the reeds 61 and 62. The poles of the biasing magnet 63, indicated by the letters N and S, are arranged so that its external flux flow which affects the reeds 61 and 62 is indicated by the broken arrows 64. The magnetic or flux circuit from the biasing magnet 63 magnetizes the reeds 61 and 62 and causes the reeds to have an attraction for each other. However, the magnetic flux of the biasing magnet alone is insuflicient to close the switch 51.

The control magnet 53 also has magnetic poles indicated by the letters N and S. The control magnet 53 is arranged so that its polar axis is generally perpendicular to the reeds 61, 62 as well as to the polar axis of the biasing magnet 63. Magnetic flux flow from the control magnet 53 is also generally indicated by the broken series of arrows 66 and 67. It is particularly noted that the flux flow 66 to the left of the control magnet 53 tends to oppose flux flow from the biasing magnet 63 while flux flow 67 to the right of the control magnet 53 travels in a manner tending to reinforce flux flow from the biasing magnet 63.

The effects on the switch 51 from leftward movement, for example, of the control magnet 53 past the switch is sequentially represented by FIGS. 4-7. While the control magnet remains at the right of the switch 51, as illustrated in both FIGS. 4 and 5, the switch 51 is generally affected only by the flux field established to the left of the control magnet 53. As noted above, this portion of the control magnet flux field opposes that of the biasing magnet 63 so that there is generally no effect upon the switch 51 and it remains in its open position. However, as the control magnet 53 commences to move leftwardly of the switch 51, as seen, for example, in FIG. 6, the switch 51 is affected by the flux field established to the right of the control magnet 53 as seen in that figure. As noted above, this portion of the control magnet flux field tends to reinforce the flux field of the biasing magnet 63 resulting in increased magnetization of the reeds 61 and 62. The strengths of the magnets 53 and 63 are selected so that their combined or reinforcing flux fields magnetize the reeds 61 and 62 and cause sufficient attraction between the two reeds so that they contact each other and the switch 51 is then closed.

As the control magnet 53 continues its leftward travel and passes out of proximity with the switch 51, it no longer has any substantial effect upon the reeds 61, 62. In this condition, the flux field of the biasing magnet is sufficiently strong so that the reeds 61, 62 tend to be held in their closed or abutting position. The ability of the biasing magnet to maintain the reeds in a closed position while being unable by itself to close the reeds, may be explained by the increased permeance between the reeds when they are contacting or abutting each other. In this condition, the magnetic flux passing through the reeds from the biasing magnet 63 causes a sufficient attraction between the reeds so that they tend to be held together in a closed position.

Effectiveness of the control magnet 53 to again open the switch 51 as it moves rightwardly past the switch 51 in close proximity thereto may be understood from considering the converse operating sequence represented by FIGS. 4-7. For example, as the control magnet moves rightwardly through the position indicated in FIG. 7 and into the position indicated at FIG. 6, only the reinforcing portions of the control magnet flux field effect the switch 51. Accordingly, the switch 51 tends to remain in its closed position. However, as the control magnet 53 moves further to the right, for example, to the position indicated in FIG. 5, portions of the control magnet flux field 66 tend to act upon the switch 51 in opposition to the flux field 64 of the biasing magnet 63. For this position of the control magnet, the flux fields tend to balance or cancel each other so that the attraction between the reeds 61 and 62 is reduced and they again return to their open position as indicated in FIGS. 5 and 4. As the control magnet continues its rightward motion past the position indicated in FIG. 4, it again has no effect upon the switch 51 so that the switch 51 remains in its open position.

A variation 50 of the switch assembly 50 is illustrated in FIGS. -13. Portions of the proximity switch assembly 50 which correspond to portions of the proximity switch assembly 50 are indicated by similar primed numerals. It will be noted that for both the proximity switch assemblies 50 and 50, the polar axis of the control magnet 53 and 53 is arranged in perpendicular relation to the reeds 61, 62 or 61, 62' as well as to the polar axis of the biasing magnet 63 and 63. However, in the switch assembly 50, the biasing magnet 63 and the reeds 61, 62 are arranged parallel to the path along which the control magnet 53 moves. In switch assembly 50, they are arranged in perpendicular relation to the same path of travel. Since the control magnets 53 and 53 are both arranged with their polar axis in perpendicular relation to the switch 51 or 51' and the biasing magnets 63 or 63, the switch reeds 61, 62' tend to be magnetized by movement of the control magnet 53' therepast in the same manner as described above for the switch assembly 50. Thus, operation of the switch assembly 50' as sequentially represented by FIGS. 10-13 is similar to the manner of operation described above with respect to FIGS. 4-7.

Another variation of the proximity switch assembly is indicated at 50" in FIGS. 8 and 9. Similar components of the switch assembly 50" are also indicated by similar double primed numerals. It will be apparent that the components of the switch assembly illustrated in FIGS. 8 and 9 are arranged in generally similar relation as for the switch assembly illustrated in FIGS. 4-7. However, it is noted that the polarity of the biasing magnet 63" has been reversed in the switch assembly 50". Thus, for the sequence of operation described with respect to FIGS. 4-7, the switch 51" operates in a manner exactly opposite from that of the switch 51. A comparison of these two sets of figures indicates that by merely reversing the polarity of the biasing magnet 63, the switch 51 may be caused to function as either a normally closed or a normally open switch within the same operating environment. In this regard, a normally open switch refers to one which when closed, completes a circuit so that a desired function is performed. On the other hand, a normally closed switch is one which performs a desired function upon being opened.

To further illustrate the manner in which these variations of the switch assembly may be employed, for example, in the control circuit for the loader bucket of FIG. 1, reference is now made to FIGS. 2 and 3. The circuit illustrated in FIG. 2 may be employed to operate a loader bucket control circuit similar to that of FIG. 1. For example, the circuit in FIG. 2 includes a DC source 54', switches 56' and 57', and solenoid 46' similar to those illustrated in FIG. 1. However, the circuit of FIG. 2 is further adapted for controlling a bucket of a conventional type having an ejector which is to be actuated for assistance in unloading of the bucket (seen at 12 in FIG. 1).

The ejector (not shown) operating circuit is closed by actuation of a second solenoid valve 71. Thus, in the circuit shown in FIG. 2, the solenoid 46 is connected in series with the normally open proximity switch assembly 50. The ejector solenoid 71 is connectedin electrical series with a normally closed switch indicated at 50". Both the switch assemblies 50 and 50" are responsive to a single control magnet 53. From the above description, it is apparent that with the control magnet 53 being positioned to the right of the two switch assemblies, the switch assembly 50 is open and the switch assembly 50" is closed. As the control magnet 53 moves slightly to the left of the two switch assemblies, the switch 50 is then closed and the switch 50 is opened. Accordingly, the switch assembly 50 has a similar operating sequence as that described above with respect to FIGS. 4-7 while switch assembly 50" has the converse or opposite operating sequence as referred to with respect to FIGS. 8 and 9.

In a typical operating sequence for bucket loaders employing this combined circuit, the switch 51 is closed and the switch 51" is open when the bucket is in the position illustrated in FIG. 1. The switch assembly 50 operates in the same manner as described above with respect to FIG. 1. However, the switch assembly 50" is closed only as the bucket approaches a forwardly pivoted position suitable for dumping. Thus, the ejector cannot be operated while the bucket is racked back or pivoted counterclockwise from the position shown in FIG. 1. In this manner, the ejector may be prevented from dumping material over the back of the bucket 12 and onto the vehicle 11 while the bucket is in its carry position.

The circuit illustrated in FIG. 3 includes a proximity switch assembly employed with components similar to those in FIGS. 1 and 2. The switch assembly 100 includes a control magnet 101 similar to the control magnet 53 of FIG. 4 and a switch 102 including reeds 103 and 104 generally similar to the reeds 61 and 62 of switch 51. However, different biasing means are shown in association with the switch 102. In this embodiment, the biasing means comprises an electrically conductive coil 106 which encompasses the reeds 103, 104 of the switch 102. Current flow through the coil is selected to induce a magnetic field having north and south poles, as indicated by the letters N and S respectively, equivalent to those for the biasing magnet 63 illustrated, for example, in FIGS. 4-7. Thus, the switch assembly 100 operates in a generally similar manner as the switch 50 described with respect to FIGS. 4-7.

Still another variation of the switch assembly is indicated at in FIGS. 14-18. The switch assembly 150 includes a switch 151 made up of reeds 152, 153 similarly as the switch 51 of FIG. 4. A biasing magnet 154 is associated with the switch 151 also in a similar manner as for the biasing magnet 63 of FIG. 4, for example. However, in this switch assembly, a plurality of control magnets are employed, for example, those indicated at 156 and 157. The two control magnets 156 and 157 may be mounted on a single member such as the extendible rod 17 illustrated in FIG. 1. The arrangements and relative spacing shown for the control magnets are selected to permit sequential operation of the switch 151 as the two control magnets move past the switch in a single direction. The control magnets 156 and 157 are both arranged with their polar axis in perpendicular relation to the reeds 152, 153 and the polar axis of the biasing magnet 154. However, it is noted that the magnetic poles or polarity of the two control magnets are reversed with respect to each other. Thus, whereas the control magnet 156 operates in generally an identical manner as the control magnet 53 of FIG. 4, the reversed control magnet 157 will have exactly the opposite efiect upon the switch 151. For example, FIGS. 14-18 sequentially represent operation of the switch 151 by the two control magnets 156 and 157. As the two control magnets move leftwardly past the open switch 151, the control magnet 156 first causes the switch 151 to close when the magnet 156 is in a similar position as the control magnet 53 illustrated in FIG. 6. However, as the two control magnets continue to move leftwardly in unison and the magnet 157 approaches a similar actuating position, its magnetic flux field is in opposition to that of the biasing magnet 154. Thus, the control magnet 157 again causes the switch 151 to open. it is immediately apparent that relative spacing between the two control magnets 156 and 157 may be selected to cause the switch 151 to close and again open within a selected distance of travel for the control magnet combination while both of the control magnets are moving in a single direction. Movement of the two control magnets 156 and 157 in an opposite direction also has a respectively converse efiect upon the switch 151 in the same manner as described above for the other switch embodiments.

What is claimed is:

l. A tilt control system for a bucket loader including a vehicle, at least one lift arm pivotally connected to the vehicle and an implement pivotally supported on. the lift arm, motor means being interconnected between the vehicle and lift arm for raising and lowering the implement, the tilt control system comprising,

a hydraulic tilt jack interconnected between the implement and the vehicle for rotating the implement about its pivotal connection with the lift arm,

a valve in communication with the tilt jack and having operating positions for rotating the implement in different directions, the valve including a detent mechanism tend ing to maintain the valve in at least one of its operating positions,

electrically responsive means coupled with the detent mechanism and operable to disengage the detent mechanism, and

a proximity switch assembly associated with the tilt jack and operatively coupled with the electrically responsive means, the switch assembly including a reed switch having a pair of magnetizable reeds and arranged on one portion of the tilt jack, magnetic biasing means being arranged on the one tilt jack portion adjacent the reed switch and having a polar axis parallel to the reeds, the

switch assembly also including magnetic control means arranged on another portion of the jack which is movable relative to the one jack portion during extension and retraction of the jack, the magnetic control means having a polar axis perpendicular to the polar axis of the biasing means, the arrangement of the reed switch and control means on the two tilt jack portions being selected so that the control means is in actuating register with the reed switch when the implement is rotated to a selected posi tion whereby the reed switch is opened when the control means passes thereby in one direction and closed when the control means passes thereby in the opposite direction to permit engagement of the detent mechanism with the control valve and to maintain the detent mechanism in a disengaged condition when the implement is rotated in opposite directions from its selected position by the tilt jack.

2. The tilt control system of claim 1 wherein the implement is a loader bucket arranged for loading in its selected position, the bucket being rotatable in one direction from its selected position to a carry position and in the opposite direction to an unloading position.

3. The tilt control system of claim 1 wherein the biasing means and control means are magnets.

4. The tilt control system of claim ll wherein the implement is an ejector bucket and further comprising electrically responsive means for operating the ejector, the switch assembly including a second similar reed switch and parallel biasing means effectively coupled with the electrically responsive means for operating the ejector and arranged on the one portion of the tilt jack so that it is also opened and closed by the operating means.

5. The tilt control system of claim 4 wherein the biasing means for both reed switches are magnets and the control means is a single magnet. 

1. A tilt control system for a bucket loader including a vehicle, at least one lift arm pivotally connected to the vehicle and an implement pivotally supported on the lift arm, motor means being interconnected between the vehicle and lift arm for raising and lowering the implement, the tilt control system comprising, a hydraulic tilt jack interconnected between the implement and the vehicle for rotAting the implement about its pivotal connection with the lift arm, a valve in communication with the tilt jack and having operating positions for rotating the implement in different directions, the valve including a detent mechanism tending to maintain the valve in at least one of its operating positions, electrically responsive means coupled with the detent mechanism and operable to disengage the detent mechanism, and a proximity switch assembly associated with the tilt jack and operatively coupled with the electrically responsive means, the switch assembly including a reed switch having a pair of magnetizable reeds and arranged on one portion of the tilt jack, magnetic biasing means being arranged on the one tilt jack portion adjacent the reed switch and having a polar axis parallel to the reeds, the switch assembly also including magnetic control means arranged on another portion of the jack which is movable relative to the one jack portion during extension and retraction of the jack, the magnetic control means having a polar axis perpendicular to the polar axis of the biasing means, the arrangement of the reed switch and control means on the two tilt jack portions being selected so that the control means is in actuating register with the reed switch when the implement is rotated to a selected position whereby the reed switch is opened when the control means passes thereby in one direction and closed when the control means passes thereby in the opposite direction to permit engagement of the detent mechanism with the control valve and to maintain the detent mechanism in a disengaged condition when the implement is rotated in opposite directions from its selected position by the tilt jack.
 2. The tilt control system of claim 1 wherein the implement is a loader bucket arranged for loading in its selected position, the bucket being rotatable in one direction from its selected position to a carry position and in the opposite direction to an unloading position.
 3. The tilt control system of claim 1 wherein the biasing means and control means are magnets.
 4. The tilt control system of claim 1 wherein the implement is an ejector bucket and further comprising electrically responsive means for operating the ejector, the switch assembly including a second similar reed switch and parallel biasing means effectively coupled with the electrically responsive means for operating the ejector and arranged on the one portion of the tilt jack so that it is also opened and closed by the operating means.
 5. The tilt control system of claim 4 wherein the biasing means for both reed switches are magnets and the control means is a single magnet. 